A fixed version of FlutterToast. It adds customization options to the original FlutterToast

fixed_toast.dart

import 'package:flutter/material.dart';
import 'package:toast/toast.dart';

class FixedToastView {
  static final FixedToastView _singleton = new FixedToastView._internal();

  factory FixedToastView() {
    return _singleton;
  }

  FixedToastView._internal();

  static OverlayState overlayState;
  static OverlayEntry _overlayEntry;
  static bool _isVisible = false;

  static void show(String msg, BuildContext context,
      {int duration = 1,
      int gravity = 0,
      Color backgroundColor = const Color(0xAA000000),
      textStyle = const TextStyle(fontSize: 15, color: Colors.white),
      double backgroundRadius = 4,
      Border border}) {
    FixedToastView.dismiss();
    FixedToastView.createView(msg + ' ' + msg, context, duration, gravity,
        backgroundColor, textStyle, backgroundRadius, border);
  }

  static void showCustom(Widget content, BuildContext context,
      {int duration = 1,
      int gravity = 0,
      Color backgroundColor = Colors.transparent,
      double backgroundRadius = 4,
      Border border}) {
    FixedToastView.dismiss();
    var v = Container(
        alignment: Alignment.center,
        width: MediaQuery.of(context).size.width,
        child: Container(
          decoration: BoxDecoration(
            color: backgroundColor,
            borderRadius: BorderRadius.circular(backgroundRadius),
            border: border,
          ),
          //margin: EdgeInsets.symmetric(horizontal: 20),
          //padding: EdgeInsets.fromLTRB(16, 10, 16, 10),
          child: content,
        ));
    FixedToastView._createView(v, context, duration, gravity, backgroundColor,
        backgroundRadius, border);
  }

  static void createView(
      String msg,
      BuildContext context,
      int duration,
      int gravity,
      Color background,
      TextStyle textStyle,
      double backgroundRadius,
      Border border) async {
    _createView(
        _createText(
            msg, context, background, textStyle, backgroundRadius, border),
        context,
        duration,
        gravity,
        background,
        backgroundRadius,
        border);
  }

  static void _createView(
      Widget content,
      BuildContext context,
      int duration,
      int gravity,
      Color background,
      double backgroundRadius,
      Border border) async {
    overlayState = Overlay.of(context);

    Paint paint = Paint();
    paint.strokeCap = StrokeCap.square;
    paint.color = background;

    _overlayEntry = new OverlayEntry(
      builder: (BuildContext context) => ToastWidget(
          widget: Container(
            width: MediaQuery.of(context).size.width,
            child: content,
          ),
          gravity: gravity),
    );
    _isVisible = true;
    overlayState.insert(_overlayEntry);
    await new Future.delayed(
        Duration(seconds: duration == null ? 1 : duration));
    dismiss();
  }

  static Widget _createText(String msg, BuildContext context, Color background,
      TextStyle textStyle, double backgroundRadius, Border border) {
    return Container(
        alignment: Alignment.center,
        width: MediaQuery.of(context).size.width,
        child: Container(
          decoration: BoxDecoration(
            color: background,
            borderRadius: BorderRadius.circular(backgroundRadius),
            border: border,
          ),
          margin: EdgeInsets.symmetric(horizontal: 20),
          padding: EdgeInsets.fromLTRB(16, 10, 16, 10),
          child: Text(msg, softWrap: true, style: textStyle),
        ));
  }

  static dismiss() async {
    if (!_isVisible) {
      return;
    }
    _isVisible = false;
    _overlayEntry?.remove();
  }
}